Some vehicle systems include multiple vehicles coupled together. These vehicle systems can include trains or rail vehicle consists having a brake pipe that extends along the length of the vehicle system. The brake pipe carries air used to engage or disengage air brakes of the vehicle system. When air pressure in the pipe is above a threshold, the air brakes are disengaged. When the air pressure drops below the threshold, the air brakes may be engaged to slow or stop movement of the vehicle system.
Engagement of the air brakes in multiple vehicles of the vehicle system may be coordinated by dropping the pressure in the brake pipe by a designated amount. This drop in pressure can propagate along the length of the pipe with a well-defined leading edge. As different vehicles identify the pressure drop, the vehicles engage the air brakes.
As vehicle systems become longer, the well-defined drop in pressure in the brake pipe that is used to engage the brakes may get distorted and not be detected by the vehicles that are very far from the vehicle that initiated the pressure drop. For example, if the pressure drop is initiated at a front or leading end of a train, the locomotives or rail cars at the back or trailing end of the train may not see a sharp well-defined drop in brake pipe pressure but rather a slow reducing brake pipe pressure that may result is a lower brake reduction than was initiated by the front of the train. The pressure in the brake pipe at the back or trailing end of the train may be sufficiently low that the pressure drop is undetected. As a result, the brakes of these locomotives or rail cars may not be engaged when needed.
Additionally, longer vehicle systems may introduce increased fluctuations, or noise, in measurements of the pressures in the brake pipe. These fluctuations can prevent or interfere with the detection of pressure drops used to instruct the vehicles to engage the air brakes. For example, large fluctuations can cause a vehicle to incorrectly identify noise as an instruction to engage the air brakes.